1. Field of the Invention
This invention relates to a method and apparatus for removing an elastomeric closure from a pre-filled syringe barrel, measuring the force required to remove the elastomeric closure from the pre-filled syringe barrel, and then measuring the breakaway and running forces required to move the plunger in the pre-filled syringe barrel from its proximal position toward the distal end of the barrel.
2. Reported Developments
Pre-filled syringe barrels or cartridges without an access means, such as a needle, contain injectable solutions therein. The syringe barrels or cartridges are stoppered by elastomeric closures, such as soft rubber stopper-like devices, at the distal, tapered end thereof, while the proximal end of the barrels are closed by slidable plungers. Prior to use a plunger rod is inserted into the plunger so that manual pressure can be exerted on the plunger for dispensing the injectable fluid from the barrel. The syringe barrels or cartridges are autoclaved or sterilized by other means and packaged ready for use.
The elastomeric closure in the form of a soft rubber stopper comprises a wall across the mouth opening of the tapered barrel and a plug depending therefrom which is inserted into the mouth opening of the barrel. The elastomeric closure allows easy insertion into the barrel to form a tight seal therewith and is designed to maintain the integrity of the seal during autoclaving. Removal of the elastomeric closure is often required prior to use of the injectable solution, such as for verifying that the elastomeric closure remains in place during storage and will not accidentally be removed, for testing the integrity of the injectable solution, or for measuring the breakaway and running forces necessary to move the plunger from its initial position at the proximal end of the barrel toward the distal end of the barrel. On extended shelf-life the elastomeric closure tends to develop a strong physical bond with the wall of the barrel making manual removal cumbersome. The removal of an elastomeric stopper from a glass syringe barrel carries the risk of injury to the operator since the glass may shatter when held manually.
The prior art provides for removal of closures from tubes and vials containing biological and other samples therein. The removal of such closures is often accomplished with automated sample handling systems designed to handle large number of tubes and vials. Illustrative examples of such systems are disclosed in the following references.
U.S. Pat. No. 4,068,798 discloses a method for stopper removal comprising the steps of: suspending a test tube by its stopper; and subjecting the suspended test tube to a centrifugal force to cause the tube to separate from the stopper under the influence of the centrifugal force.
U.S. Pat. No. 4,982,553 discloses an automatic apparatus for pulling out test tube stoppers. The apparatus includes a plug extracting mechanism comprising a U-shaped stationary frame having tube-clamping members to hold a tube therein; and plug-extracting cylinders having styluses which pierce the plug contained in the tube to extract the plug.
U.S. Pat. No. 5,490,321 discloses a method and apparatus for removing a stopper from a container, the apparatus comprising a container holder and claw members. The claw members are driven by a linear drive source and a swinging motion drive source. The stopper is removed from the material holding container while applying a pull-up force and twist force to the fitted stopper.
U.S. Pat. No. 4,876,926 discloses a stopper-removal apparatus which comprises: a first mechanism for gripping the container against rotation; a second mechanism for gripping the stopper; and a drive for rotating the second mechanism about an axis while the second mechanism grips the stopper. The stopper removal apparatus includes an annular ring having a plurality of small spikes non-radially aligned which grip the stopper only if the ring is rotated in one direction, and slip off the stopper when the rotating drive rotates in a direction opposite to the one direction.
It is an object of the present invention to provide a method and an apparatus for removing elastomeric closures from pre-filled syringe and cartridge barrels and to measure the force required for their removal.
It is another object of the present invention to determine the force necessary to initially move the plunger in the barrel referred to as breakaway force, and to determine the force necessary to continue movement of the plunger, variously referred to as push, gliding or running force, while maintaining the required output from the barrel.